The streaking is weird, though it may be down to the spray pattern you made. Could well be down to moisture bubbles/pockets, though on mine they were a bit more random.

It could also be dry overspray; paint that didn't go on wet but droplets which dried enough on their way from the can to stick but not merge with the rest of the paint. Sometimes down to heat, sometimes having the can too far away from the surface. This can be simply sprayed over with wet nitro as it will melt and be absorbed into the general nitro mass.

Yes, up to 28°C is probably OK without some retarder (the cans normally have a bit of retarder and anti-bloom product, but there's nothing like being able to regulate it yourself to match the conditions), but keep it out of direct sunlight as even with a light colour, the surface can become really hot and the surface of the nitro dries instantly, trapping solvent under the surface which can form bubbles. So, definitely work in the shade when it's warm.

Also let it dry in the shade, at least for the first hour or so. I've had bubbles form in clear after spraying it in too hot conditions and letting it dry in my old dark-coloured spray/toilet tent (my new one is silver-white and far more reflective), where it was well above ambient. If you get those in clear, you need to sand back as you can't spray your way out of it. I tried and failed.